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From: Hyman Rosen <hymie@prolifics.com>
Subject: Re: Ada
Date: 2000/01/04
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Date: 2000-01-04T18:36:21+00:00
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Robert A Duff <bobduff@world.std.com> writes:
> Even worse, it means that literals can't be overloaded.  Of course, C++
> doesn't even *have* enumeration literals of different enumeration types,
> anyway.

It certainly does. The problematic part is that enumeration literals
are entered into the scope in which the enumeration type is declared,
because of backward compatibility with C. As a result, one normally
declares enumerated types inside a class or namespace, so that literals
won't conflict.

If you really need enumerator literal overloading, you can play the
same game as for empty sets, on a case-by-case basis:

struct Direction { enum E { Left, Right, Up, Down }; };
struct Politics  { enum E { Left, Center, Right }; };

static struct
{
	operator Direction::E() { return Direction::Left; }
	operator Politics ::E() { return Politics ::Left; }
} Left;

static struct
{
	operator Direction::E() { return Direction::Right; }
	operator Politics ::E() { return Politics ::Right; }
} Right;

void f(Direction::E) { }
void g(Politics ::E) { }

int main()
{
	f(Left);
	f(Right);
	g(Left);
	g(Right);
}